Valves are commonly used in process control systems to control the flow of process fluids. Rotary valves (e.g., butterfly valves) typically have a closure member (e.g., a disc) disposed in a fluid path. A valve shaft operatively couples the closure member to an actuator that rotates the closure member between an open position and a closed position to allow or restrict fluid flow between an inlet and an outlet of the valve. When the closure member is in the closed position, the closure member sealingly engages a valve seat or sealing surface (e.g., a seal ring fixed to the valve body) to restrict fluid flow through the valve.
A follower shaft (which may be integrally formed with the valve shaft) is typically coupled to an end of the closure member opposite the end of the valve shaft to provide support to the closure member so that the closure member can maintain proper alignment with the sealing surface and provide a tight shut-off when the valve is in the closed position. Without a follower shaft, the closure member may deflect away from the sealing surface when the valve is in the closed position, thereby causing fluid leakage between the inlet and the outlet when the valve is in a closed position. Typically, a mechanical fastener (e.g., a pin, a weld, etc.) is employed to couple the follower shaft to the closure member. The follower shaft rotates with the closure member as the closure member moves between the first and second positions and an end cap retains the follower shaft within the valve body.
However, other than a welded connection, pins and/or other mechanical fasteners do not provide a sanitary connection between the follower shaft and the closure member, which can cause bacterial growth that can contaminate the process fluid. In some applications such as, for example, the food and beverage industry and the pharmaceutical industry, sanitary valves are often employed. Thus, sanitary valves typically include a follower shaft and a valve shaft that are coupled to the closure member via welding. However, welding a follower shaft and/or the valve shaft to the closure member requires the use of a split-body valve in order to enable assembly of the fluid valve. Split-body valves include a body liner or body seal to provide a seal and, thus, increase manufacturing complexity and costs.